THE FLOW OF WATER I2T WOOD-STAVE PIPE. 59 
less any velocity head, k v ', tkat may be recovered as tke water 
approackes tke pipe outlet at a velocity relatively kigk compared 
witk tke velocity in tke open water below tke outlet ckamber. Tkis 
total may be expressed by tke formula 
HB = h v + he + h f -h v ' (21) 
wkere H E kas tke significance skown in figure 1 and k v , ke, k f , and 
h/ kave tke significance defined on page 3. Tke influence of 
gentle curves was included in tke data upon wkick tke formulas were 
based, so tkat an additional loss for skgkt bends or curves need not 
be considered in tke design of tke usual pipe on irrigation systems. 
If skarp bends can not be avoided tken an additional loss of kead 
must be anticipated. Tke results of suck tests as kave been made 
on bends in pipes are given in standard works on kydraukcs. 
- VELOCITY AND ENTRY LOSSES. 
In designing pipes of small diameter and great lengtk, tke losses 
due to velocity and entry keads, k v and ke, are so small compared 
witk tke friction loss tkat tkey may be neglected. Otkerwise tkey 
skould be included in tke allowance for total lost kead. 
As a rule a wood-stave pipe fine begins under one of four general 
conditions : 
1. Intake ckamber located in a reservoir, wkere tke velocity of tke 
water is practically zero. No taper or transition section between 
intake and pipe. 
2. # Intake ckamber located on an open ckannel wkere tkere is an 
appreciable velocity toward tke structure but wkere tkis velocity 
is not available because a bend or well at tke intake practically 
dissipates tke velocity kead. 
3. Intake ckamber followed by a transition section in wkick tke 
velocity is increased over tkat existing in tke leading ckannel or 
reservoir. Tke outlet end of a pipe beginning imder tkis condition 
is usually provided witk a similar transition section. 
4. Tke wood pipe but a continuation of anotker pipe of tke same 
size but of concrete, steel, or otker material. In this case tkere is 
kttle or no loss due to entry or velocity, tke only factor introduced 
being tke ckange in friction kead due to ckange of material. 
In conditions 1 and 2 it is best to consider tke water above tke 
intake as at rest. From tkis state of rest velocity must be created and 
increased to tke mean velocity, V, existing in tke pipe. Tke kead, 
h v , necessary to create a given velocity is skown in column 2, Table 5. 
Tke entry loss will be from 0.5 k v wkere tke pipe of standard size 
begins at a keadwall and is witkout bell or taper moutk, to about 
0.25 h v for a rounded intake, and 0.05 k v for a bell-moutk intake. 
Many of tke structures built by tke United States Reclamation 
